Alternate bar response to sediment supply termination
Bibliographic record
Abstract
Sediment supply is widely held to be one of the primary controls on bar topography in alluvial channels, yet quantitative linkages between sediment supply and bar topography are not well developed. We explore the conditions under which alternate bars form and how they respond to the elimination of sediment supply in two linked laboratory experiments. The first set of experiments was conducted in a 28 m long, 0.86 m wide flume channel using a unimodal sand‐gravel mix. The second set of experiments was conducted at field scale in a 55 m long, 2.74 m wide channel using a unimodal gravel mixture. In both experiments, alternate bars and patchy surface grain‐size distributions developed under steady flow and sediment supply conditions. The cessation of the sediment supply induced a reduction in the surface grain‐size heterogeneity and the bars were eliminated. In both flumes, mean boundary shear stress had declined, but were capable of moving sediments after the bars disappeared, albeit at relatively small rates compared to when the bars were present. In the smaller flume, the previously stationary bars migrated out of the flume and were not replaced with new bars. A nearly featureless bed formed with limited surface grain‐size heterogeneity, a slightly coarsened surface and a slightly reduced slope. In the larger flume, the formation of alternate bars was induced by an imposed upstream flow constriction and as such, the bars did not migrate. Termination of sediment supply led to progressive erosion of bed topography and loss of the bars, coarsening of the bed surface, loss of bed texture patchiness and significant slope reduction. The original alternate bar topography redeveloped when the sediment supply was restored once sufficient deposition had occurred to reconstruct the original channel slope. This shows that the bar loss was reversible by establishing the previous conditions and highlights the importance of sediment supply for bar formation. The role of sediment supply in bar formation and stability is not often recognized in stream restoration. Our results suggest that the loss of sediment supply can significantly affect alternate bar topography and that considerable volumes of sediment may be needed restore channel bars.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".